1. Field of the Invention
This invention concerns a method of manufacturing a semiconductor crystalline layer and, more particularly, it relates to a method of manufacturing a semiconductor crystalline layer, which comprises forming a polycrystalline or amorphous semiconductor layer on a substrate in which a relatively thick insulation layer is formed on one main surface of semiconductor single crystals, melting the semiconductor layer by scanning continuously oscillating laser beams, for example, argon laser beams to the semiconductor layer and thereby forming a semiconductor single crystalline layer on the insulation layer from the underlying semiconductor crystals as the seeds.
2. Description of the Prior Art
Various improvements and studies have been made generally for semiconductor integrated circuits (IC) for reducing the size, simplifying the structure and improving the performance of various equipments However, there is an inevitable limit to the technique for integrating such semiconductor devices at high density on a plane, that is, in a 2-dimensional manner. In view of the above, research and development have been conducted for semiconductor devices having features in the 3-dimensional structure in recent years. As the basis for the development of such 3-dimensional semiconductor devices, various developments have been attempted to the techniques for forming semiconductor crystalline layer on one main surface of semiconductor single crystals as the seeds.
FIG. 1 shows one example of conventional methods for growing a semiconductor crystalline layer as shown in the descriptions of "Single Crystal Silicon-on-Oxide by a Scanning CW Laser Induced Lateral Seeding Process" (presented by H. W. Lam, R. F. Pinizzotto and A. F. Tasch, Jr.) disclosed in "J. Electrochem Soc.: SOLID-STATE SCIENCE AND TECHNOLOGY" September 1981, pp 1981-1986.
In the figure, a structure comprising a single crystalline silicon substrate 1 having {100} face [(001) face or crystal face equivalent thereto] as the main surface (hereinafter simply referred to as a silicon substrate),a relatively thick oxide insulation layer 2 composed of a silicon dioxide membrane formed on one main face of the silicon substrate 1 and a polycrystalline silicon layer 3 formed on the oxide insulation layer 2 by way of chemical vapor deposition process (hereinafter simply referred to as CVD process) is used as the substrate in the manufacture of single crystalline membrane. The single crystalline silicon layer 3S is formed by scanning the continuously oscillating laser beams 5 relative to the polycrystalline silicon layer 3 while irradiating them and scanning in the direction of the arrow X and melting and recrystallizing the polycrystalline silicon layer 3. Accordingly, the single crystalline silicon layer 3S is formed into single crystals along the direction of the main face of the silicon substrate 1.
FIGS. 2A through 2D are cross sectional views illustrating the manufacturing steps of a semiconductor employed as a substrate in the conventional manufacturing step for a single crystal membrane. Explanation will be made to the method of manufacturing a semiconductor device used as the substrate while referring to FIGS. 2A through 2D.
In FIG. 2A, the silicon substrate having {100} face as the main face is at first exposed to an oxidizing atmosphere at 950.degree. C. to form thermally oxidized membrane 7 of 500 .ANG. thickness on the main face and then a silicon nitride membrane 8 is formed to a thickness of about 1000 .ANG. by using CVD process.
In FIG. 2B, the silicon nitride membrane 8 was removed while leaving only those portions corresponding to the opening on the silicon substrate 1, eliminating other portions of the silicon nitride membrane by means of photolithography and etching.
In FIG. 2C, the exposed thermally oxidized membrane 7 is removed by using the patterned silicon nitride membrane 8 as a mask and, further, the surface of the silicon substrate 1 is eliminated by about 5000 .ANG. through etching. Then, by exposing the silicon substrate 1 to an oxidizing atmosphere at 950.degree. C. for a long time, an oxide insulation layer 2 composed of silicon dioxide of about 1 .mu.m thickness is grown on a predetermined region.
In FIG. 2D, the silicon nitride membrane 8 left at the surface of the silicon substrate 1 and the thermally oxidized membrane 7 therebelow are eliminated, and a polycrystalline silicon layer 3 is grown to a thickness of about 7000 .ANG. by using a CVD process. In this way, there is formed a substratum 10 comprising the silicon substrate 1 having {100} face as the main face, a thick oxidized insulation layer 2 formed on the silicon substrate 1 and having the opening 6 reaching the underlying silicon substrate at least to a portion thereof and the polycrystalline layer 3 formed on the opening 6 and the oxidized insulation layer 2.
Then, description will be made of the method of forming a single crystalline silicon layer on an oxidized membrane (insulation membrane) using the substratum 10 formed by the steps shown from FIG. 2A through FIG. 2D while referring to FIG. 1.
As shown in FIG. 1, by melting the polycrystalline silicon layer 3 above the opening 6 by the irradiation of the laser beams 5 and extending the melting to the surface of the silicon substrate 1 below the opening 6, epitaxial growing results from the single crystals in the underlying silicon substrates as the seeds upon recrystallization to reform the polycrystalline silicon layer 3 into single crystal. Accordingly, upon melting the polycrystalline silicon layer 3 by scanning the laser beams 5 in the direction of the arrow X in FIG. 1, epitaxial growing results continuously in the lateral direction, that is, in the scanning direction of the laser beams 5 thereby enabling to growth of the single crystalline layer 3S on the oxidized insulation layer 2 as the insulation layer.
However, in the method of forming the single crystalline silicon layer, there is a problem that the power distribution of the laser beams 5 has an extremely significant effect on the melting and recrystallization in the polycrystalline silicon layer 3.
FIGS. 3A and 3B are views illustrating the power distribution of the laser beams used for melting the polycrystalline silicon layer, as well as the solid-liquid boundary and the crystal growing direction upon melting the polycrystalline silicon. More specifically, FIG. 3A shows the power distribution characteristics of the laser beams, while FIG. 3B shows the crystal growing direction of the polycrystalline silicon layer on a plane.
As shown in FIG. 3A, the power distribution of the laser beams 5 used for melting the polycrystalline silicon layer 3 forms a so-called Gaussian type distribution in which the power is higher at the lateral center of the beams and lower at the peripheral area in the lateral direction perpendicular to the scanning direction of the laser beams shown by the arrow X. Accordingly, in the case where the polycrystalline silicon is melted and then recrystallized, solidification starts from the periphery of the molten portion at low temperature and the crystal growth prevails toward the center of the molten portion at high temperature. Accordingly, as shown in FIG. 3B, crystal growth from various crystal nuclei at the periphery of the beam width results at the solid-liquid boundary 12. As a result, since the crystal growing directions 13 are not constant and the epitaxial crystal growth along the face direction of the main face of the silicon substrate 1 is hindered, the region in which the grown layer of the single crystal silicon 3S is obtained has been restricted to 50 or 100 .mu.m from the end of the opening 6 in the conventional method as described above.
In order to overcome the foregoing problems, an attempt has been made to extent the distance of the epitaxial crystal growth by forming stripe-like reflection preventive membranes on the upper portion of the polycrystalline silicon layer 3, resulting in a periodic temperature distribution in the lateral direction (relative to the laser scanning direction shown by the arrow X) within the polycrystalline silicon layer 3 upon irradiation of the laser beams.
As an example of the method of growing single crystal while controlling the temperature distribution of the laser beams by the use of the reflection preventive membrane as described above, there has been disclosed "Use of selective annealing for growing very large grain silicon on insulator films" [Appl. Phys. Lett. 41(4), Aug. 15, 1982, pp 346-347] presented by J. P. Colinge, et al in "American Institute of Physics 1982". In this literature, the temperature distribution of the spot laser is shown in FIG. 1 and the photograph showing the reflection preventive membrane and the manner of crystal growth is shown in FIG. 2 respectively. As another example different from that described in the foregoing proceedings, there can be mentioned "Method of manufacturing a semiconductor single crystalline layer" filed by one of the present inventors on Dec. 13, 1982 to Japanese Patent Office and laid-open by the director general of Japanese Patent Office on June 22, 1984 (Japanese Patent Laid-Open No. Sho 59-108313).
FIGS. 4A through 4C show the details of the latter prior art. In the drawings, parts and portions identical with those in FIGS. 1, 2, 3A and 3B are represented by identical reference numerals.
Stripe-like reflection preventive membrane 15 having stripe portions 15a the longitudinal direction of which extend in &lt;110&gt; direction or the direction equivalent thereto are formed on a polycrystalline silicon layer. The reflection preventive membrane 15 has a function of preventing laser beams from reflecting in the region and making the temperature of the polycrystalline silicon layer 3 below the region in which the stripe portions 15a are formed higher than the temperature of the polycrystalline silicon layer 3 at the region in which no stripe portions 15a of reflection preventive membrane are formed. By disposing such reflection preventive membrane 15, a periodic temperature distribution as shown in FIG. 5B can be formed within the polycrystalline silicon layer 3 upon irradiating the laser beams 5. In FIG. 5B, the abscissa represents the position in the polycrystalline silicon membrane and the ordinate shows the temperature upon irradiating the laser beams.
When the stripe-like reflection preventive membrane 15 are disposed and the laser beams 5 are irradiated along the longitudinal direction of the stripe portions 15a of the reflection preventive membrane 15 while scanning them along the direction of the arrow X, since a periodic temperature distribution is formed along the lateral direction (relative to the scanning direction of the laser beams) in the polycrystalline silicon layer 3, the crystal growing directions 13 are directed from the center of the region in which no stripe portions 15a of the reflection preventive membrane 15 are formed to the region of the polycrystalline silicon layer 3 in which the stripe portions 15a of the reflection preventive membrane 15 are formed. Since the reflection preventive membrane 15 reaches as far as the opening 6, the epitaxial growth from the underlying substrate single crystal below the opening 6 as the seeds continuously occurs from the opening 6 to the polycrystalline silicon layer 3 at a low temperature on the oxidized insulation layer 2. Accordingly, for the growth of the recrystallized silicon layer 3S on the oxidized insulation layer 2, epitaxial crystal growth results only along the phase direction of the underlying silicon substrate 1 from the opening 6 and, as a result, the crystal growing direction is made constant (uni-direction) and the single crystal growing direction can be increased.
However, also in this case, although the crystal growing distance can be extended in the case where the scanning speed of the laser beams 5 is from 1 to 5 cm/sec, if the scanning speed of the laser beams 5 is increased to 20 or 30 cm/sec in order to increase the output (processing amount), the single crystal growing distance is restricted to about 200 .mu.m from the end of the opening 6.
In a conventional silicon wafer used as the silicon single crystal substrate 1, since the orientation flat face for the detection of the position is disposed to the (110) face, all of the patterns formed on the wafer (patterns for the chip arranging direction, circuit elements formed on the chips) are restricted to the directions parallel with or perpendicular to the &lt;110&gt; direction, that is, the intersecting direction between the orientation flat face and the silicon wafer or the direction equivalent thereto and, accordingly, the longitudinal direction of the stripe of the reflection preventive membrane 15 is also restricted to the direction parallel with the &lt;110&gt; direction or the direction equivalent thereto. Accordingly, in the case of scanning the laser beams 5 in the &lt;110&gt; direction or the direction equivalent thereto, the actual crystal growing direction determined by the temperature distribution set by the stripe of the reflection preventive membrane 15 is greatly different from &lt;110&gt; direction which is the scanning direction of the laser beams 5. Thus, it is greatly deviated also from {111} face in which stabilized crystal growth is obtained. In the case where the scanning speed for the laser beams 5 is slow, since the transition region for the actual melting-solidification to the deviation between the crystal growing face and {111} face is broad, the range capable of allowing the deviation is also extended. However, in the case where the scanning speed for the laser beams 5 is high, the range capable of allowing the deviation is narrower resulting in crystal defects such as laminar defects and thereby resulting in crystal boundary subsequently. Accordingly, there has been a problem that no long single crystal growing can be obtained in the recrystallized single crystalline silicon layer.